Dream plot, but TAFF house - first mistake already made

Warehouses??? Workshop???
Is that a mixed-use area? Who covers the demolition costs?
What kind of (former) workshop is it? How long has it existed, what was there before? Which company, which trade?

The seller is tearing everything out completely, making the boundaries visible, removing the concrete floor, etc., so everything is fine. It was a metal construction workshop, existed for many years, and went bankrupt due to a generational change. It is a residential area, but I will ask again.

In metal processing, the floor becomes contaminated. Solvents are used, and tiny metal chips get stuck. In the past, it seems that not only in the West, but also in the East ( ops: ) everything was drained into the ground. Just try googling it. Without an expert report, they can go to hell!

To what extent does this manifest? The property is (except of course for the driveway to the hall) quite well covered with grass... the neighboring properties are also very green. Numerous ants and fire beetles swarm there, so you can hardly see anything from the outside.

Metal construction workshop, existed for decades

And who told you that it was non-toxic?

... I will bring up the topic with the toxicological report

To what extent does this manifest? The property is quite well covered with grass (except, of course, in the driveway to the hall)...

That is the problem. In the end, you will only notice it when the children play in the garden, or when you eat vegetables from your own cultivation, or when you simply mow the lawn. Poisoning with heavy metals occurs very gradually. You also can't see oils and other substances on a lawn.

The handling of environmentally hazardous substances used to be much more lax; unfortunately, many of these substances do not decompose by themselves.

the neighboring properties are also very green

It is a residential area

Are there already houses on the left and right, or are the areas still undeveloped?